engleski

Optimization of extraction conditions of total phenolic compounds from wheat grain using response surface methodology

Response surface methodology (RSM) was applied to optimize the extraction conditions of total phenolic compounds from wheat grain. Tested samples were collected from three silos at different locations of Croatia: Kutjevo (WK), Čakovec (WC) and Beli Manastir (WB), and represent an average harvest of wheat in 2011/2012. A Box Behnken design was used to investigate the effects of solvent concentration (30-90% aqueous ethanol), extraction temperature (30 90 °C) and time (10- 70 min) as well as their interaction on the extractability of total phenolic compounds. The total phenolic content (TPC) in extract was determined by spectrophotometric Folin- Ciocalteau micro method at 765 nm and results were expressed as gallic acid equivalent per a dry basis of wheat grain (mgGAE/gdb). RSM analysis showed that solvent concentration and temperature had significant effect, while effect of time and interaction of factors on the observed extraction process were not significant. The optimal conditions for extraction of phenolic compounds were found to be 58 % aqueous ethanol, 83 °C and 70 minutes. Under these conditions, the experimental results of TPC (WK: 3.67 mgGAE/gdb, WC: 3.33 mgGAE/gdb and WB: 3.41 mgGAE/gdb) were close to the predicted values (3.7 mgGAE/gdb, 3.26 mgGAE/gdb and 3.35 mgGAE/gdb, respectively) calculated from the polynomial response surface model equation.

optimization of extraction ; response surface methodology ; wheat grain ; total phenolic compounds

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